If you think you would go to your local GP's Saturday surgery we would advise you to check.

The Saturday surgery used to be a staple of British medical life.

It may have been just a few hours on a Saturday morning, but it helped fill the gap from Friday night until Monday morning.

Today finding a local GP whose surgery opens on Saturday is hard work.

Nobody in my position had ever believed we could pull it off - but to get it for 6% was a bit of a laugh

Dr Simon FraddBritish Medical Association

If you go on the NHS website you can search for doctors who open their surgeries on Saturday.

According to the website there are 100 Saturday surgeries in London alone.

The Radio 4 series "The Investigation" called every one of the GPs on the list to find if they really did still open on Saturdays.

The results were clear: only eight of the surgeries actually did so. In total there are 1,300 GP practices in London.

New contract

So what is the reason for the strange disappearance of Saturday surgeries?

The main culprit is the new GP contract, brought in during 2004.

I think it is always easy to underestimate how strongly GPs respond to an incentive that gives them money

Dame Gill MorganNHS Confederation

This deal gave GPs a huge pay rise. The average GP now earns £106,000 a year.

But what gets less coverage is that it also ended GP responsibility for out of hours services.

Previously GPs had what was known as the John Wayne contract, which meant whatever the hour, "a GP's gotta do what a GP's gotta do".

This was understandably not popular with doctors but they never thought the issue was negotiable.

According to one of the GPs' lead negotiators, Dr Simon Fradd, during talks on the new contract the NHS Confederation and the government made it clear that they were prepared to let GPs give up out of hours work.

Negotiations then started on how much it would cost GPs to withdraw from responsibility for evenings and weekends.

Doctors surprised

Dr Fradd thought the government might extract a high price from the doctors for such a big reduction in working hours.

He thought it could even have been as much as 50% of earnings, which the profession would have rejected. But when it came to the final deal GPs got a much better price.

"We got rid of it for effectively 6% of the value of the contract. It was just stunning.

"Nobody in my position had ever believed we could pull it off but to get it for 6% was a bit of a laugh."

This was certainly a good deal for GPs, who could now work office hours for the bargain price of a roughly £6,000 cut in salary. But was it good value for taxpayers?

Big cost

The only evidence so far is from the National Audit Office. It found the government underestimated how much it would cost the NHS. In the first year it was an extra £70 million - 20% more than anticipated.

One of the unfortunate side effects of the new contract has been that doctors have reined in their opening hours

Dr Anthony Burch

The NAO found the most difficult time for out of hours was Saturday morning.

There is certainly a demand for Saturday surgeries.

When the government asked people in a survey what would most improve their ability to see a GP, almost two thirds said Saturday surgeries. So why didn't the contract stipulate that they continued?

The NHS Confederation is the employers' organisation which negotiated the deal with the GPs on behalf of the government.

Its chief executive Dame Gill Morgan, who used to be a GP herself, says it never realised quite how much impact the deal would have.

"I don't think anybody thought that people would just wipe out the Saturday services because that was always open for people to continue to do.

"I think we were surprised to see how many people stopped the Saturday services," she told the programme.

Highly valued service

There are still a few surgeries that open on Saturday, offering a service that is highly appreciated by their patients.

If you visit the Staverton surgery in North West London any Saturday you will see there is a queue waiting for the doors to open at 10am.

Dr Anthony Burch regularly sees 30 patients in one morning session.

Other doctors tell him he is mad to continue with a service that he does not have to provide, but he thinks Saturdays are important.

"We like working office hours but lots of patients find they can't go to the doctors during office hours so you have to balance that," he says.

"I know that we are providing something that our patients value.

"One of the unfortunate side effects of the new contract has been that doctors have reined in their opening hours and I think that is one of the things that the Department of Health is probably regretting now."

The NHS Confederation hopes that more GPs will open Saturday surgeries, but it has no real way to make them do so.

Too many sweeteners

Looking back on the new contract, its Chief Executive Dame Gill Morgan feels there were too many sweeteners in the deal offered to GPs.

"I think it is always easy to underestimate how strongly GPs respond to an incentive that gives them money," she says.

The government is currently surveying 5 million patients and asking them if they would like GPs to open on Saturdays.

It is perhaps a shame they didn't consult the public before they agreed the deal that killed off Saturday opening in the first place.

The Investigation will be broadcast on BBC Radio 4 on Thursday 1 February at 20:00 GMT.